A study of pontecorvo reactions in antiproton deuterium annihilations at rest

Summary  The results of the analysis of a new data sample of $$\bar p$$ annihilations at rest on deuterium and hydrogen, taken at the CERN LEAR by the OBELIX spectrometer, are presented. The $$\bar p$$ d → π−p channel has been measured with a noticeable reduction of both the statistical and the systematic errors with respect to the previous OBELIX measurement and the branching ratio turns out to be (1.29±±0.07(stat)±0.05(syst))·10−5, in good agreement with the previous result. The $$\bar p$$ d→ρ−p→π−π0p channel has been investigated for the first time and the branching ratio is evaluated to be (2.9±0.4(stat)±0.5(syst))·10−5. Finally, as a check of the spectrometer absolute calibration, the $$\bar p$$ p→π+π− channel was also studied with a measured branching ratio of (4.27±0.15(stat)±0.17(syst))·10−3, in good agreement with the ASTERIX result.